In many communications networks used today, a message may—by the nature of the network, the devices and protocols involved, or other factors—be broadcast to all recipients on the network prepared to receive it, such as all set top boxes in a cable network, all browsers being used to view of an online live media platform like Facebook® Live or Twitch®, or all radios tuned to a given station. Historically, many communications networks have had this property, ranging from telegraph networks to ethernet networks.
Lack of ability to differentiate among recipients leads to inefficiency from the point of view of the recipient (for example, receiving an emergency alert over the radio that does not apply to the listener), as well as the broadcaster (for example, the broadcast's nature typically only allowing one message to be transmitted to the entire audience at a given time). Additionally, a broadcaster typically has no way of knowing which recipients or devices are currently receiving the broadcast, or any characteristics of the broadcast's current audience.